The unusually strong force behind the apocalyptic fires in Los Angeles

Sustained powerful winds reaching nearly 100 miles per hour are driving fast-moving wildfires near Los Angeles, spewing smoke, destroying homes, closing roads, and forcing thousands of people to evacuate. 

The Palisades fire along the coast near the Santa Monica mountains has burned more than 5,000 acres as of Wednesday afternoon. The Eaton fire near Pasadena has now torched at least 2,200 acres. The blazes have killed at least two people and destroyed more than 1,000 structures. Other smaller fires are also burning in the region. 

These blazes are stunning in their scale and speed, jumping from ignition to thousands of acres in a day, but they’re hardly unexpected. Fire forecasters have been warning since the beginning of the year that conditions were ripe for massive infernos, particularly in Southern California. “For January, above normal significant fire potential is forecast across portions of Southern California,” according to a National Interagency Fire Center (NIFC) bulletin on January 2. 

“This was an exceptionally well-predicted event from a meteorological and fire-predictive services perspective,” Daniel Swain, a climate scientist at the University of California Los Angeles, said Wednesday during a livestream. 

The winter months are typically when Southern California quenches its thirst with rainfall, but the past few weeks have been unusually dry, and little snowfall has accumulated in the surrounding mountains. The NIFC also noted that temperatures were “an impressive two to six degrees [Fahrenheit] above normal in most areas” in December, allowing vegetation like grasses and chaparral to readily dry out and serve as fuel. 

On top of this, the Santa Ana winds, Southern California’s seasonal gusts, were unusually strong. They typically blow from the northeast toward the coast in the wintertime, but this year, an unusually warm ocean and a meandering jet stream are giving these gales an additional speed boost, like pointing a hair dryer at Los Angeles. 

Firefighters are working desperately to corral the flames and keep them away from people’s homes, but there’s little they can do to halt the combination of ample fuel, dry weather, and high winds, which are poised to continue. It will take another force of nature to quell this one. “Until widespread rains occur, this risk will continue,” according to the NIFC bulletin. 

Wildfires are a natural part of the landscape in California, but the danger they pose to the region is growing because more people are living in fire-prone areas. That increases the likelihood of igniting a blaze and the scale of the damage that occurs when a fire inevitably erupts. California’s growing wildfire threat has rocked the state’s insurance industry and forced regulators to allow insurers to price in the risk of worsening future catastrophes.  At the same time, global average temperatures are rising due to climate change, which can prime more of the landscape to burn. 

It will take a concerted effort on many fronts to mitigate the wildfire threat, including using more fire-resistant building materials, performing controlled burns to reduce fuels, changing where people live, improving forecasting, pricing insurance in line with the actual disaster risk, and reducing greenhouse gas emissions that are driving climate change. 

But in the meantime, the dangers from fires in Southern California are likely to get worse.

What are the Santa Ana winds? Why are they so powerful this year?

Parts of California regularly experience persistent high winds during certain times of year. The northern part of the state, including the San Francisco Bay Area, tends to see high winds in the spring and fall known as the Diablo winds. 

Southern California’s Santa Ana winds often arise in the winter months. “This is not a typical Santa Ana, but this is the time of year when you expect it,” Swain said. 

The mechanisms behind the Santa Ana and Diablo winds are similar: Cool air from inland mountains rolls downhill toward the coasts. That air compresses as it moves to lower altitudes and squeezes between canyons, heating up and drying out, similar to a bicycle pump. But there are several factors that may be worsening these gusts right now.

One is that the band of the Pacific Ocean near Southern California remains unusually warm following two years of record-high temperatures all over the world that triggered underwater heat waves. High temperatures in the ocean can bend the jet stream. This is a narrow band of fast-moving air at a high altitude that snakes across the planet and shapes the weather below. As it meanders, it can hold warm air under high pressure in place, allowing heat to accumulate closer to the surface. When high pressure settles over inland areas like the Great Basin northeast of Los Angeles, it starts driving air over the mountains and toward the coast. 

What’s making fires so bad right now? 

Again, wildfires are a natural and vital mechanism in the ecosystem in Southern California. They help clear decaying vegetation and restore nutrients to the soil. But people are making the destruction from wildfires far worse. 

The majority of wildfires in the US are ignited by humans — careless campfires, sparks from machinery, downed power lines — but there are also natural fire starters like dry lightning storms and on rare occasions, spontaneous combustion of decaying vegetation and soil. The ignition sources of the current fires around Los Angeles aren’t known yet. 

The population in the region is also expanding, although the growth rate has recently slowed down. More people in the area means more property, and in Southern California, that property can be quite expensive. As the fires move toward populated areas, they can do a lot of damage.  

“I do expect it is plausible that the Palisades fire in particular will become the costliest on record,” Swain said. 

The weather this year has also left abundant vegetation in the region that has desiccated in the warm, dry air. And of course, humans are heating up the planet by burning fossil fuels and that is enhancing some of the raw ingredients for dangerous fires. 

Ample fuel plus high wind in unusually dry weather near a major population center have converged to create an extraordinary and dangerous spate of wildfires. 

What’s the role of climate change?

Many factors have to converge to start a massive wildfire, and the variables aren’t all straightforward. In recent years, California has been ping-ponging between extremely dry and wet years. That’s had a strong impact on the vegetation in Southern California. Unlike the forests in the northern part of the state that grow over the course of decades, the amount of grass and brush around Los Angeles can shift widely year to year depending on precipitation. 

“There is a very high degree of background variability,” Swain said. The key thing to pay attention to is the sequence of extreme weather. Last winter, the Los Angeles area was soaked in torrential downpours that set new rainfall records. The deluge helped irrigate a bumper crop of grasses and shrubs in the area. The region then experienced some of its all-time hottest temperatures followed by one the driest starts to winter ever measured. 

These swings between extreme rainfall and drought have been dubbed weather whiplash, and climate scientists expect these shifts to become more common along the West Coast, and that could increase the threat of major blazes. 

“It’s not just that drier conditions are perpetually more likely in a warming climate, it’s that this oscillation back and forth between states is something that is particularly consequential for wildfire risk in Southern California,” Swain said.